ABSTRACT
The bacterial deacetylase LpxC is a promising target for the development of antibiotics selectively combating Gram-negative bacteria. To improve the biological activity of the reported benzyloxyacetohydroxamic acid 9 ((S)-N-hydroxy-2-{2-hydroxy-1-[4-(phenylethynyl)phenyl]ethoxy}acetamide), its hydroxy group was replaced by a triazole ring. Therefore, in divergent syntheses, triazole derivatives exhibiting rigid and flexible lipophilic side chains, different configurations at their stereocenter, and various substitution patterns at the triazole ring were synthesized, tested for antibacterial and LpxC inhibitory activity, and structure-activity relationships were deduced based on docking and binding energy calculations.
Subject(s)
Amidohydrolases/antagonists & inhibitors , Anti-Bacterial Agents/chemical synthesis , Bacterial Proteins/antagonists & inhibitors , Enzyme Inhibitors/chemical synthesis , Hydroxamic Acids/chemical synthesis , Triazoles/chemistry , Anti-Bacterial Agents/pharmacology , Cycloaddition Reaction , Enzyme Inhibitors/pharmacology , Gram-Negative Bacteria/drug effects , Humans , Hydroxamic Acids/pharmacology , Microbial Sensitivity Tests , Molecular Docking Simulation , Molecular Structure , Stereoisomerism , Structure-Activity RelationshipABSTRACT
Many allosteric binding sites that modulate gamma aminobutyric acid (GABA) effects have been described in heteropentameric GABA type A (GABAA) receptors, among them sites for benzodiazepines, pyrazoloquinolinones and etomidate. Diazepam not only binds at the high affinity extracellular "canonical" site, but also at sites in the transmembrane domain. Many ligands of the benzodiazepine binding site interact also with homologous sites in the extracellular domain, among them the pyrazoloquinolinones that exert modulation at extracellular α+/ß- sites. Additional interaction of this chemotype with the sites for etomidate has also been described. We have recently described a new indole-based scaffold with pharmacophore features highly similar to pyrazoloquinolinones as a novel class of GABAA receptor modulators. Contrary to what the pharmacophore overlap suggests, the ligand presented here behaves very differently from the identically substituted pyrazoloquinolinone. Structural evidence demonstrates that small changes in pharmacophore features can induce radical changes in ligand binding properties. Analysis of published data reveals that many chemotypes display a strong tendency to interact promiscuously with binding sites in the transmembrane domain and others in the extracellular domain of the same receptor. Further structural investigations of this phenomenon should enable a more targeted path to less promiscuous ligands, potentially reducing side effect liabilities.
Subject(s)
GABA-A Receptor Antagonists/chemistry , GABA-A Receptor Antagonists/pharmacology , Protein Domains/drug effects , Receptors, GABA-A/metabolism , Allosteric Regulation/drug effects , Animals , Benzodiazepines/chemistry , Benzodiazepines/pharmacology , Binding Sites/drug effects , Drug Design , Humans , Ligands , Models, Molecular , Quinolones/chemistry , Quinolones/pharmacology , Receptors, GABA-A/chemistry , gamma-Aminobutyric Acid/metabolismABSTRACT
GABAA receptor modulators are structurally almost as diverse as their target protein. A plethora of heterocyclic scaffolds has been described as modulating this extremely important receptor family. Some made it into clinical trials and, even on the market, some were dismissed. This review focuses on the synthetic accessibility and potential for library synthesis of GABAA receptor modulators containing at least one heterocyclic scaffold, which were disclosed within the last 10 years.
Subject(s)
GABA-A Receptor Agonists/chemical synthesis , GABA-A Receptor Antagonists/chemical synthesis , Heterocyclic Compounds/chemical synthesis , Receptors, GABA-A/chemistry , Small Molecule Libraries/chemical synthesis , Allosteric Regulation , Animals , Clinical Trials as Topic , GABA-A Receptor Agonists/pharmacology , GABA-A Receptor Antagonists/pharmacology , Heterocyclic Compounds/pharmacology , Humans , Molecular Structure , Small Molecule Libraries/pharmacology , Structure-Activity RelationshipABSTRACT
Allosteric ligands of GABAA receptors exist in many different chemotypes owing to their great usefulness as therapeutics, with benzodiazepines being among the best known examples. Many allosteric binding sites have been described, among them a site at the extracellular interface between the alpha principal face and the beta complementary face (α+/ß-). Pyrazoloquinolinones have been shown to bind at α+/ß-binding sites of GABAA receptors, exerting chiefly positive allosteric modulation at this location. In order to further explore molecular determinants of this type of allosteric modulation, we synthesized a library of ligands based on the PQ pharmacophore employing a ring-chain bioisosteric approach. In this study we analyzed the structure-activity-relationship (SAR) of these novel ligands based on an azo-biaryl structural motif in α1ß3 GABAA receptors, indicating interesting novel properties of the compound class.